Its extremely important to check your backup if its working.
We just had a customer that lost three months worth of data. He had a backup system for 15k (...) that never backed anything up.
When his hard drive broke 2 weeks ago and he had to send it to a lab, In the end they could not save the complete file. They sent us pieces of the file and we reconstructed alot of the data. (The charges and payments we saved.)
Besides of the hours we put in to it (in this busy season) he now needs to go thru alot of records and re-enter alot of stuff in between.
The only reason he did have data from 3 months ago was because we had a copy from then.
So please make sure to check that your backup is actually working.